MR started from branch that has been branched from another one will be merged anyway

Summary

Unexpectedly, MR started from branch that has been branched from another one will be merged anyway. If has failed pipeline or marked with WIP - it does not matter.

Steps to reproduce

  1. Select any project you want.
  2. Create branch old-branch, make some changes, commit and push it to the branch.
  3. Create MR MR-old to merge old-branch to master, assign it to yourself (for convenience). Mark it with WIP, you can even add CI support and create pipeline that make job to fail. So you will have MR, marked with WIP and with failed pipeline.
  4. Create another branch new-branch from old-branch, make some changes, commit and push it to the branch. Branch tree should be:
master --

         \-- old-branch------

                        \--new-branch
  1. Create MR MR-new to merge new-branch to master, assign it to yourself (for convenience). This MR must be mergable.
  2. Accept MR-new.

What is the current bug behavior?

MR-new' will be merged, MR-old(WIP, failed pipeline) will be merged too, branchold-branch` will stay.

What is the expected correct behavior?

MR-new' will be merged, MR-old(WIP, failed pipeline) will not be merged too, branchold-branch` will stay.

Relevant logs and/or screenshots

I reproduce it on gitlab.com, you can see it in my test project: https://gitlab.com/rusbik91/testproject/merge_requests/3 https://gitlab.com/rusbik91/testproject/merge_requests/4